Cloning application servers to create a cluster can be a valuable
asset in configuring highly scalable production environments, especially when
the application is experiencing bottlenecks that are preventing full CPU utilization
of symmetric multiprocessing (SMP) servers.
When adjusting the WebSphere Application Server system queues in clustered
configurations, remember that when a server is added to a cluster, the server
downstream receives twice the load.

Two servlet engines are located between a Web server and a data source.
It is assumed that the Web server, servlet engines and data source, but not
the database, are all running on a single SMP server. Given these constraints,
the following queue considerations must be made:
- Double the Web server queue settings to ensure ample work is distributed
to each Web container.
- Reduce the Web container thread pools to avoid saturating a system resource
like CPU or another resource that the servlets are using.
- Reduce the data source to avoid saturating the database server.
- Reduce Java heap parameters for each instance of the application server.
For versions of the Java virtual machine (JVM) shipped with WebSphere Application
Server, it is crucial that the heap from all JVMs remain in physical memory.
For example, if a cluster of four JVMs is running on a system, enough physical
memory must be available for all four heaps.